In modern window cleaning systems, washer fluid pumps of said type are often mounted on a washer fluid container and are known from practice. The ventilation duct which leads to a ventilation opening serves for acclimatization and pressure equalization of the housing which at least partially holds the electric motor, and is for example guided straight through the housing. Here, the ventilation opening must be large enough to permit an infiltration of air into the housing and an outflow of air out of the housing. An excessively small ventilation opening tends to become blocked, which often leads to a pressure build-up and to damage of sealing elements between the electric motor and the pump stage or to foreign objects being sucked into the interior of the electric motor. An excessively large ventilation opening, in contrast, leads to an infiltration of spray water into the electric motor. In both cases, the washer fluid pump can be destroyed and spontaneously fail.
It has already been considered to guide the ventilation duct radially out of the housing and to arrange a bulkhead in front of the ventilation opening. This however leads to very complex production of the washer fluid pump. Furthermore, it is for example possible for spray water to pass behind the bulkhead and infiltrate into the ventilation duct. Here, the fluid passes directly into the electric motor.